[C++知识库]c++重载++ -- 输入输出运算符

#include <iostream>
using namespace std;

class people {
   // friend ostream& operator <<(ostream& out, const people p1);
   /* friend people& operator ++(people& p1);
    friend people& operator ++(people& p1, int wuyong);*/// 什么时候加上友元函数声明 比如需要访问类中私有类成员 否则不用添加 
public:
int age;
    int num;
    people(int age,int num)
    {
        this->num = num;
        this->age = age;
    }
    ~people() {

    } 
    people& operator ++() {
        (this->age)++;
        (this->num)++;
        return *this;
    }
    
};
  ostream& operator <<(ostream &out, const people& p1)//输出运算符重载

   {
        out << "p1的值" << p1.age << endl;
        return out;
   }
  istream& operator >>(istream& ifs,  people& p1) {//重载输入运算符
      ifs >> p1.age;
      ifs >> p1.num;
      return ifs;
  }
  people& operator ++(people& p1) {//前置++数重载据类型利用非成员函数实现
      p1.age++;
      p1.num++;
      return p1;
  }
  people& operator ++(people& p1, int wuyong) {//后置++运算符重载利用非成员函数重载
      people temp(p1.age, p1.num);
      p1.age++;
      p1.num++;
      return temp;
  }
  people& operator --(people& p1, int wuyong) {//后置--运算符重载利用非成员函数重载
      people temp(p1.age, p1.num);
      p1.age--;
      p1.num--;
      return temp;
  }
int main()
{
    people p1(2,3);
    cin >> p1;
    cout << p1.age << endl;
    
}